Instrumentation and Methods for Astrophysics
Towards High-Throughput Visible Photonic Lanterns for the EMARCOT Project
Abani Shankar Nayak, Julius Goehring, Marina Centenera-Merino et al. (+14 more)
Photonic EMARCOT is an innovative project involving Spanish, German and Australian research institutes that aims to integrate multiple Optical Tube Assemblies (OTAs) using photonic lanterns. The "Pathfinder" prototype, featuring seven OTAs with a 1.1-meter effective aperture, will feed a spectrograph at the Calar Alto Observatory, with first light expected in 2026. We report the fabrication and experimental evaluation of a custom 7x1 multi-mode photonic lantern (MMPL) developed for this framework, featuring seven 25 um core multi-mode inputs merging into a single 50 um core multi-mode output optimized for the visible wavelength range (400-700 nm). Optical characterization centered at 600 nm reveals exceptional channel-to-channel uniformity, with statistical variations close to zero across both bare-fiber and connectorized MMPL configurations. However, the total baseline throughput of this initial device was limited to below 4%. From the refractive index studies, this low throughput is attributed to severe refractive index mismatch between the internal fiber cladding geometry and the structural capillary, which suppresses total internal reflection during the tapering transition. This work establishes an important diagnostic baseline that highlights the necessary fabrication tolerances needed to improve future high-throughput manufacturing processes for precision radial-velocity astronomy.
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All authors Abani Shankar Nayak, Julius Goehring, Marina Centenera-Merino, Pedro José Amado-González, David Pérez-Medialdea, Mabel Ruiz-Lopez, Francisco J. Pozuelos, Miguel Andrés Sánchez Carrasco, José Luis Ortiz Moreno, Jesús Aceituno-Castro, Stefan Cikota, Javier Flores, Christopher Betters, Andrew Ross-Adams, Sergio Leon-Saval, Martin M. Roth, Kalaga Madhav
Instrumentation and Methods for Astrophysics
Magnetising the quokka code with fast, second-order accurate, error-correcting schemes for magnetohydrodynamics on GPUs
Neco Kriel, Elizabeth Cole-Kodikara, Benjamin Wibking et al. (+4 more)
We implement a second-order accurate constrained transport (CT) magnetohydrodynamics (MHD) module with first-order flux correction in the open-source, adaptive mesh refinement (AMR), GPU-accelerated code quokka, supporting both ideal and resistive (constant Ohmic) regimes. For computing and averaging the electromotive forces (EMFs) at
cell edges, the basis of any CT-MHD method, we experiment with a wide range of recent, state-of-the-art schemes, together with different reconstruction schemes. Alongside these, we develop a new EMF compute scheme that requires fewer reconstruction steps than existing approaches. We evaluate these scheme combinations on the basis of accuracy, stability, and GPU throughput, and demonstrate that our new scheme achieves accuracy comparable to the best-in-class existing methods, together with greater stability in reconnection-dominated flows and roughly 25–60% higher GPU throughput. Using this scheme, quokka achieves excellent results across a wide range of MHD flow regimes, reaching >50 million
cell updates per GPU per second, with >70% parallel efficiency out to >500 GPUs. Finally, we confirm that our CT implementation preserves divergence-free
magnetic fields (to machine precision) under AMR.
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All authors Neco Kriel, Elizabeth Cole-Kodikara, Benjamin Wibking, Mark R. Krumholz, Chong-Chong He, Anish Sarkar, Pak Shing Li
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
Fast and Furious: Long-term orbit integrations with collocation integrator Lobbie
Dmitrii E. Vavilov, Siegfried Eggl and Sarah Greenstreet
Efficient and accurate numerical integration methods are fundamental to studying long-term solar system dynamics, where numerical errors can accumulate over billions of orbital periods. In this work, we investigate the performance of our modification of Lobbie, a Lobatto collocation integrator for long-term simulations of the Solar System. We compare Lobbie against the widely used WHFast symplectic integrator and the high-order adaptive collocation integrator IAS15 implementations in the Rebound package. The performance of the integrator is evaluated using five
benchmark problems: a circular two-body orbit integrated over 100 Myrs, two-body orbits with eccentricities up to 1-10^{-6} to test the adaptive step size control during repeated close encounters, the full eight-
planet Solar System integrated over 100 Myrs, the four giant
planets integrated over 10 Gyrs, and the eight-
planet Solar System together with 50 asteroids on Aten-like orbits integrated over 1Myr to test the integrator's consistency in a chaotic, close-encounter-rich environment. Across all tests, Lobbie demonstrates excellent long-term stability and competitive computational performance. For full Solar System integrations, Lobbie achieves relative energy conservation at the level of 10^{-14} while outperforming IAS15 in computational efficiency and approaching the speed of WHFast at comparable accuracy. In the Solar System plus asteroids test, Lobbie also keeps different realizations of Jupiter's orbit consistent with each other to within about 1.5 km after 1 Myr of integration, two orders of magnitude better than IAS15, being twice faster. Our results demonstrate that Lobbie provides a powerful universal alternative to traditional symplectic mappings or Gauss-Radau collocation methods for long-term dynamical simulations in celestial mechanics.
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Instrumentation and Methods for Astrophysics
Instrument-Level Validation of Upper Sideband Syntonization Concept
Volodymyr Kudriashov and Manuel Martin-Neira
Upper Sideband Syntonization (USBS) is a two-way frequency-transfer concept proposed by the European Space Agency for distributed space
radio interferometric systems. Previous investigations validated the concept primarily through frequency-stability and phase-transfer measurements. This work demonstrates the first end-to-end instrument-level validation of the USBS concept through coherent W-band cross-correlation measurements and image reconstruction. A P=2 USBS breadboard was integrated with a W-band
radio interferometer developed for this test. The synchronized local oscillators (LOs) were evaluated through long-term cross-correlation measurements and coherent imaging of a point-like noise source. The results were compared with those obtained using a conventional common LO as well as two independent free-running LOs. The USBS-derived LOs maintained coherence over 500 s of cumulative effective integration time acquired over approximately five days of elapsed time and preserved inter-session phase stability over measurements spanning 40 days. The reconstructed image is nearly indistinguishable from that obtained with a common LO, whereas independent free-running LOs lead to severe coherence degradation, image distortion, and approximately 38 dB loss of peak response. The results demonstrate that USBS preserves the interferometric coherence required for W-band imaging and present the first end-to-end instrument-level validation of the USBS syntonization concept for future distributed space
radio interferometric missions
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR
UX Men: Detached Eclipsing Binary as a Benchmark Candidate
Ganesh N. Pawar, Krzysztof G. Hełminiak, Nicola J. Miller et al. (+5 more)
We present ultra-precise fundamental parameters for the detached eclipsing binary UX Men based on 31 TESS sectors ($\sim$882 d) and radial velocities from HARPS, FEROS, CORALIE, and UCLES. The light curves were detrended for spot-induced variability and modelled independently with JKTEBOP and ALLESFITTER, while radial velocities were extracted via TODCOR and fitted with a Keplerian orbit. Spectral disentangling yielded individual component spectra analysed with iSpec to determine $T_{\rm eff}$ and $\mathrm{[M/H]}$. Multi-band photometry was used to determine the fluxes, flux ratios and ultimately to measure photometric $T_{\rm eff}$. We obtain the masses $M_{\rm A}$ = $1.2300 \pm{0.0012}$ M$_{\odot}$, $M_{\rm B}$ = $1.1946\pm{0.0012}$ M$_{\odot}$ and radii $R_{\rm A}$ = $1.3605\pm{0.0031}$ R$_{\odot}$, $R_{\rm B}$ = $1.2801\pm{0.0069}$ R$_{\odot}$ with sub-percent precision. Uncertainties were found to be dominated by systematic effects coming from (weak) stellar activity. $T_{\rm eff,A}$ = $6302\pm{77}$, $T_{\rm eff,B}$ = $6292\pm65$ &
Metallicity estimates are $[M/H]_{\rm A} = 0.02\pm{0.13}$ dex and $[M/H]_{\rm B}= 0.07\pm{0.10}$ dex. Isochrone fitting yields a consistent age of $\tau$ = $2.75\pm{0.13}$ Gyr. The system exhibits a $\sim$ 673-day periodicity in eclipse-timing variations, likely due to stellar activity, with no evidence for a third body. Results are independent of the modelling code used, but without proper treatment of activity-induced systematics the uncertainties would be underestimated. UX Men is a high-precision
benchmark binary providing stringent tests of stellar models and a robust calibration source for PLATO. Expanding the sample of well-characterised detached eclipsing binaries will strengthen the empirical foundations for stellar physics and the calibration of future photometric missions
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All authors Ganesh N. Pawar, Krzysztof G. Hełminiak, Nicola J. Miller, Frédéric Marcadon, Ayush Moharana, Tilaksingh B. Pawar, Anish Kalsi, Maciej Konacki
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR
Solar Flare Prediction Using a Hybrid Convolutional Neural Network and Transformer Model
Mason Cao and Junwei Zhao
Solar
flares are intense bursts of electromagnetic radiation that occur when stored
magnetic energy in the Sun's atmosphere is suddenly released. They are categorized into five classes – from least to most powerful: A, B, C, M, and X – with each successive class representing a ten-fold increase in energy output. The electromagnetic radiation emitted by the stronger classes (C, M, and X) is capable of causing significant disruptions to communication systems, satellites, and power grids on Earth. Accurate prediction of solar
flares is crucial for mitigating their adverse effects and ensuring the functionality of critical infrastructure. This research introduces a novel model named ResNet-
Transformer, which combines a convolutional neural network (CNN), ResNet50, with a standard
Transformer architecture. The hybrid model effectively processes both spatial and time-series data derived from solar images to predict the occurrence, class (C, M, and X), and probability of solar
flares within 24-hour, 36-hour, and 72-hour windows. This hybrid deep learning model represents the first of its kind in the domain of image-based, multiclass solar
flare prediction. We evaluated the model's performance using a comprehensive set of metrics, including weighted precision, recall, and F1 score, together with balanced accuracy, the Matthews correlation coefficient (MCC), Cohen's kappa, and the area under the receiver operating characteristic curve (ROC-AUC). Results show that ResNet-
Transformer surpasses traditional machine learning methods, such as support vector machines (SVMs) and standalone CNN models, across all evaluated metrics. This study highlights the potential of integrating convolutional neural networks with
Transformers to enhance predictive capabilities in solar physics, paving the way for more reliable and timely solar
flare forecasting.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.optics
New Method for Path-length Equalization of Long Single-mode Fibers for Interferometry
M.Anderson, J. D. Monnier, K. Ozdowy et al. (+2 more)
The ability to use single mode (SM) fibers for beam transport in optical interferometry offers practical advantages over conventional long
vacuum pipes. One challenge facing fiber transport is maintaining constant differential path length in an environment where environmental thermal variations can lead to cm-level variations from day to night. We have fabricated three composite cables of length 470 m, each containing 4 copper wires and 3 SM fibers that operate at the astronomical H band (1500-1800 nm). Multiple fibers allow us to test performance of a circular core fiber (SMF28), a panda-style polarization-maintaining (PM) fiber, and a lastly a specialty dispersion-compensated PM fiber. We will present experimental results using precision electrical resistance measurements of the of a composite cable beam transport system. We find that the application of 1200 W over a 470 m cable causes the optical path difference in air to change by 75 mm (+/- 2 mm) and the resistance to change from 5.36 to 5.50 {\Omega}. Additionally, we show control of the dispersion of 470 m of fiber in a single polarization using white light interference fringes ({\lambda}c=1575 nm, {\Delta}{\lambda}=75 nm) using our method.
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All authors M.Anderson, J. D. Monnier, K. Ozdowy, J. Woillez, G. Perrin
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.HE
Teglon: A Pixel-Level Pipeline for Galaxy-Informed Gravitational-Wave Follow-up Planning and Efficiency Analysis
D. A. Coulter, P. Darc, C. D. Kilpatrick et al. (+4 more)
We describe Teglon, an open-source database and analysis pipeline engineered to optimize the search for electromagnetic (EM) counterparts to gravitational wave (GW) sources. Teglon constructs a 3D
galaxy completeness metric from an input
galaxy catalog and convolves it with the 3D localization volume of a GW event, producing an updated posterior map informed by known
galaxy distributions. Using Teglon, users can ingest arbitrary instrument footprints — or download them directly from the Treasure Map — to generate dynamic observation plans that seamlessly interpolate between targeted
galaxy pointing and region tiling. By focusing efforts on high-probability volumes, Teglon significantly reduces the predicted search area to find EM counterparts and increases observational efficiency, especially for small field-of-view (<= 1 deg^2) instruments like the Nancy Grace Roman Space
Telescope. Furthermore, Teglon integrates with Redback to calculate pixel-level model detection efficiencies, enabling custom, event-specific observing strategies or retrospective detection efficiencies on an arbitrary grid of EM transient models. Teglon also supports custom science cases, such as prioritizing Active Galactic
Nuclei searches for EM counterparts to binary black hole mergers. Having supported
Gravity Collective and related programs from the LIGO-Virgo-KAGRA third observing run (O3) through O4, Teglon is being continuously developed to support O5 and beyond. We document the public repository lineage and packaging, and provide Version 2.0 as an open-source tool for the community.
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All authors D. A. Coulter, P. Darc, C. D. Kilpatrick, R. J. Foley, P. McGill, S. D. Wyatt, R. Hausen
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
Sorting a mess I: Addressing velocity-axis correlation of cross-correlation functions. A census of atomic and ionised species in KELT-9b's atmosphere
Nicholas W. Borsato, Brian Thorsbro, Jens Hoeijmakers et al. (+3 more)
Ultra-hot Jupiters (UHJs) are the most extreme class of close-in gas giants. We combine 13 transit observations of KELT-9b from six high-resolution spectrographs spanning 316-960 nm to conduct a census of atomic and ionised species in its atmosphere using cross-correlation. We introduce an agnostic strategy to mitigate velocity-axis correlation bias in parameter uncertainties. A forward model of the cross-correlation function (CCF) and a Monte Carlo bootstrap of flux uncertainties measure the CCF-derived velocity profiles of individual species and assess their time dependence. The stellar reference frame is determined, yielding Vsys = -17.99 +/- 0.04 km s^-1 and v sin i = 110.54 +/- 0.05 km s^-1. All previously reported species are recovered except Tb II; the combined analysis detects 29 species, including C I, Si I, K I, V II, Co I, Zr II, La II, Pr II, and Nd II. All 29 recovered species exceed the conventional 5 sigma threshold in the bootstrap Mahalanobis significance test. The collective Doppler shifts show a blueshift of Delta Voffset = -8.02 +/- 0.17 km s^-1 relative to the stellar rest frame, indicating a net day-to-night wind, with no explicit time dependence when all species are homogenised. These results provide a catalogue of detections and retrieved Doppler parameters for a companion study of KELT-9b.
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All authors Nicholas W. Borsato, Brian Thorsbro, Jens Hoeijmakers, Daniel B. Zucker, Stefan Pelletier, Bibiana Prinoth
Instrumentation and Methods for Astrophysics
The CHIME/FRB Outriggers: Commissioning the Hat Creek Outrigger and an Updated Calibration Scheme for Mitigating RFI
Mattias Lazda, Nina V. Gusinskaia, Gurman Sachdeva et al. (+25 more)
This work presents commissioning of the Hat Creek Outrigger (HCO), a dual-polarization 256-element
radio interferometer that is part of the Canadian Hydrogen Intensity Mapping Experiment Fast
Radio Burst (CHIME/FRB) Outrigger project. Driven by a complex
radio-frequency interference (RFI) environment that consistently contaminates $\sim40\%$ of HCO's usable bandwidth, we implement an improved calibration scheme using Gaussian Process Regression to recover complex gain solutions over RFI contaminated channels. To validate our method, we test the performance of the array using known transients and continuum sources over relevant timescales used for fast-transient research ($\lesssim$ seconds). We find that our updated calibration scheme results in a $\sim1.69\times~\mathrm{to}~1.87\times$ improvement in the array's point-source sensitivity, while simultaneously maintaining noise properties consistent with thermal statistics. As a result, we find that the array performs consistently within theoretical expectations across $\gtrsim80\%$ of HCO's bandpass. We further observe an improvement in the interferometric performance after applying recently developed spatial filtering techniques for RFI mitigation, which rely on accurate calibration solutions for effective removal of unwanted interference. We conclude that our approach provides a valid framework for improving calibration solutions over RFI contaminated channels for large-$N$ interferometric arrays more broadly. Our work motivates future development of more sophisticated techniques to recover astrophysical information in RFI-contaminated channels, departing from the historical practice of discarding them outright.
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All authors Mattias Lazda, Nina V. Gusinskaia, Gurman Sachdeva, Shion Andrew, Juan Mena-Parra, Mandana Amiri, Bridget C. Andersen, Alyssa Atkinson, Kevin Bandura, Alice P. Curtin, Matt Dobbs, Ian Hendricksen, Jason W.T. Hessels, Danté M. Hewitt, Victoria M. Kaspi, Kholoud Khairy, Afrokk Khan, Ronniy C. Joseph, Adam E. Lanman, Calvin Leung, Kiyoshi W. Masui, Aaron B. Pearlman, Alexander W. Pollak, Vishwangi Shah, Kaitlyn Shin, Seth R. Siegel, Haochen Wang, Tarik J Zegmott
Instrumentation and Methods for Astrophysics
A data processing pipeline for the WINTER near-infrared surveyor using the $\texttt{mirar}$ framework
Viraj Karambelkar, Robert Stein, Danielle Frostig et al. (+18 more)
We present the data reduction and transient detection pipeline for the Wide-field Infrared Transient Explorer (WINTER) surveyor and report its on-sky performance. The WINTER camera utilizes cost-effective InGaAs sensors as alternatives to traditional IR sensors, and is mounted on a dedicated 1-m robotic
telescope at Palomar Observatory. The WINTER camera has six detectors producing a combined field-of-view of 1.2 sq. deg. equipped with y, J, and shortened-H bands. WINTER saw first light in June 2023 and has been operating robotically since. The WINTER data processing pipeline ($\texttt{winterdrp}$) has been implemented within the broader framework $\texttt{mirar}$: a modular, open-source $\texttt{python}$ package developed for realtime processing of images from time-domain surveys. $\texttt{winterdrp}$ performs end-to-end data processing implementing data reduction and image subtraction to go from raw dithered WINTER images to transient alerts in the $\texttt{avro}$ format, which are then sent to $\texttt{SkyPortal}$ for vetting and follow-up. During a year of observations in 2024, WINTER achieved J-band median 5-$\sigma$ depths ranging from $18.1-18.8$ mag (AB) on its six detectors in 960 second integrations as part of its survey, with an astrometric accuracy of $\approx0.2$ arcsec (a fifth of a pixel) and a detector-performance limited photometric accuracy ranging from $\approx0.09-0.18$ mag for its six detectors. We present early science results from WINTER, which include the identification of a stellar merger in M31, dust-enshrouded outbursting young stellar objects and classical novae in the Galactic plane, NIR followup of known
supernovae, and multi-messenger follow-up of
neutrinos, gravitational waves, fast X-ray transients and gamma-ray bursts.
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All authors Viraj Karambelkar, Robert Stein, Danielle Frostig, Saarah Hall, Mansi M. Kasliwal, Tomás Ahumada, Michael W. Coughlin, Thomas Culino, Kishalay De, Sulekha Kishore, Theophile Jegou du Laz, Nathan P. Lourie, Geoffrey Mo, Tanishk Mohan, Sam Rose, Benjamin R. Roulston, Aditya Pawan Saikia, Mallika Sheshadri, Robert A. Simcoe, Jamie Soon, Aswin Suresh
Instrumentation and Methods for Astrophysics
More than half of recent astronomy papers are written with language-model assistance
Serat M. Saad and Yuan-Sen Ting
Language models leave a distinctive vocabulary in the prose they help write, and we measure how much of the astronomy literature now carries it. From the full text of 207,111 astro-ph papers spanning 2015 to mid-2026, we count those words in each paper and model the counts, in proportion to paper length, as a mixture of assisted and unassisted writing in a hierarchical
Bayesian model. Papers from before 2020 calibrate the unassisted rate, and the 392 papers that disclose model use calibrate the assisted one. Our answer depends on how often these words would appear today if nobody used a model, a rate that must be modeled rather than observed, so we extend it past 2020 under three assumptions and report all three. For 2025 that gives $54^{+8}_{-8}\,(\mathrm{stat},\,95\%)\,^{+26}_{-0}\,(\mathrm{sys,\ background})$% of papers, the second error being the spread across the three. The estimate stays at or above 36% when we vary that choice, the calibration, and the requirement that adoption only rises. A word list built from the astro-ph corpus, keeping only words that rose across every subfield, leaves 2025 in the same range. Assisted writing is also getting harder to see, since authors adapt to the words that reveal it and the marker excess more than halves between 2023 and 2026. Our model allows for that fading, so it can separate a fainter trace from reduced use. More than half of recent astro-ph papers therefore carry a
language-model trace, while only 0.81% of 2025 papers disclose it, one declaration for every $\sim$66 papers with a trace.
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Instrumentation and Methods for Astrophysics
Small-Body Science with the Nautilus Space Observatory: From Cislunar Space Resilience to Mapping the Kuiper-Belt-to-Oort-Cloud Transition
J. de Wit, A. Y. Burdanov, P. McGill et al. (+3 more)
A new generation of space-based observatories can transform small-body science from the local Earth-Moon environment to the Solar System's dynamical frontier, where planetary control gives way to Galactic tides and stellar encounters. Mapping this frontier would reveal how planetesimals were scattered during giant-
planet formation, how many primordial bodies survived in distant reservoirs, and whether large objects remain undiscovered in the inner Oort Cloud. At the same time, meter- to decameter-scale natural objects traversing the Earth-Moon system are frequent but poorly characterized. As human and robotic activity expands, their operational relevance depends not simply on abundance but on object size, encounter geometry, exposed infrastructure, warning time, and available response. Lunar impacts and impact-generated ejecta provide one class of events, while fading objects with unresolved Earth or lunar impact probabilities provide another. Here, we explore a two-layer small-body program combining a 4.0 m-diameter Nautilus Quattro Imaging (NQI) unit with an illustrative distributed cislunar layer of ~50 cm-class wide-field optical
telescopes. The cislunar layer would characterize the nearby natural-object population, support rapid classification and selective custody of high-interest objects, and monitor lunar impacts and ejecta; the NQI deep-search layer would provide precise astrometry and synthetic tracking for faint-object recovery and distant-Solar-System surveys. Together, the two layers would constrain the small-impactor population, resolve fading planetary-defense targets, and survey the distant Solar System to Vmag ~30, enabling tests of the Kuiper-Belt-to-Oort-Cloud transition while advancing Earth-Moon space resilience.
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All authors J. de Wit, A. Y. Burdanov, P. McGill, D. Apai, S. N. Hasler, S. Cambioni
Instrumentation and Methods for Astrophysics
Performance Comparison of the Nonlinear Curvature and Shack-Hartmann Wavefront Sensors in Strong Turbulence
Sam J. Potier, Arlene J. Aleman, Justin R. Crepp et al. (+1 more)
Strong
turbulence induces spatial variations in beam intensity that hinder the reconstruction process of many commonly deployed adaptive optics (AO) systems that use gradient-based wavefront sensors (WFS), such as the Shack-Hartmann wavefront sensor (SHWFS) and pyramid wavefront sensor. The nonlinear
curvature WFS (nlCWFS) uses Fresnel diffraction to extract wavefront phase and amplitude information, suggesting that it may be able to operate under challenging
turbulence conditions. In this work, we investigate nlCWFS reconstruction accuracy as a function of
turbulence strength and relative flux by modeling high spherical-wave Rytov number ($R_{sw}$) environments where scintillation and branch points impact sensing performance. We present open-loop as well as static and dynamic closed-loop results benchmarked against a comparable Shack-Hartmann WFS (SHWFS). In static and weak-to-moderate scintillation regimes, the nlCWFS consistently outperforms the SHWFS by leveraging amplitude-phase coupling inaccessible to gradient-based sensors. However, dynamic closed-loop simulations reveal a crossover behavior at higher scintillation strengths, where deep intensity nulls and proliferating branch points degrade the performance of Gerchberg-Saxton-based nlCWFS reconstruction, while the SHWFS degrades more gradually due to its insensitivity to such topological phase structure. These results highlight the regime-dependent advantages of the nlCWFS and emphasize the need for branch-point-tolerant reconstruction
algorithms to fully realize its potential in strong-
turbulence, low-flux conditions.
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All authors Sam J. Potier, Arlene J. Aleman, Justin R. Crepp, Stanimir Letchev
Instrumentation and Methods for Astrophysics
Beyond the BLUE I: the advantage ceiling - how much can any estimator beat the matched filter in mm/submm survey data?
Kaustuv Basu
Papers claiming that convolutional neural networks outperform the matched filter are now common in astronomy. Since that filter is the best linear unbiased
estimator (BLUE) for any noise of given covariance, and the minimum-variance unbiased
estimator under Gaussian noise, such a claim requires that the noise covariance varies from image to image or the noise is non-Gaussian. We introduce the advantage ceiling eta >= 1, which quantifies both cases: the Fisher information for the amplitude in units of the matched filter's, computable from noise-only simulations before any network is trained, and a bound on the variance of any
estimator unbiased at each true amplitude. We compute eta for a suite of millimeter/submillimeter survey noise models and for compact and extended source templates, using a variational score-matching ladder whose rungs are
estimator classes of increasing statistical order, from linear to convolutional. With an instrumental white-noise floor, Gaussian noise returns eta = 0.94-1.06 (+-0.04); covariance mixtures give exact ceilings of 10.2 (spectral tilt, extended source), 2.1 (leaked components) and 1.1-1.8 otherwise; residual artifacts give eta <= 1.09. Source confusion gives the largest advantage, eta >= 3.8 (extended) and >= 2.4 (compact). Three unmodelled channels - a zeroed DC mode, a missing white floor and floating-point rounding - can manufacture spurious advantages of up to two orders of magnitude. A ResNet regressor is 6-15% less efficient than the matched filter on Gaussian noise once prior shrinkage is divided out, and realizes a factor 1.8 of the 10.2 available on the spectral-tilt mixture; a companion paper tests such regressors against these ceilings.
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Instrumentation and Methods for Astrophysics
Wide Field Localization Using Fixed Modulation Collimators
Steven E. Boggs
Rapid, precise localization of gamma-ray bursts (GRBs) requires continuous wide-field imaging at hard X-ray and soft gamma-ray energies. We develop a fixed (non-rotating) modulation-collimator architecture to address this challenge. A bigrid collimator, a pair of aligned, periodic slit grids in front of a simple, non-imaging
photon-counting detector, transmits an off-axis source through a triangular fringe pattern whose local angular position, the source phase, is recovered from simultaneous count rates in several grid pairs at fixed relative phase offsets, rather than by mechanically rotating a single grid pair as in the classical rotating modulation collimator. Four-phase demodulation of these count rates robustly cancels detector background and grid leakage without requiring rotation. Because the fringe pattern repeats across the sky, a phase measurement corresponds to many candidate source positions; we resolve this ambiguity over an arbitrarily wide field of view using a cascade of progressively coarser-pitched grid stages, generalizing the two-grid vernier-scale technique originally used to localize Sco X-1. This vernier cascade technique reduces the required
photon counts and grid-calibration accuracy required to achieve fine angular resolution over a broad field of view. Generalized to two dimensions with orthogonal cascades, the resulting architecture achieves wide-field localization with no moving parts, no time modulation, and only simple
photon-counting detectors, a promising candidate for simple, inexpensive, continuous-monitoring instruments supporting time-domain and multi-messenger astrophysics.
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Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
A Differentiable Parametric Model of Binary-Black-Hole Initial Data: I. Conformally flat Bowen-York punctures
Frederik De Ceuster and Tjonnie G.-F. Li
Constraint-satisfying initial data for binary black holes require the repeated solution of a nonlinear elliptic boundary-value problem throughout the physical parameter space. We present a para\-metric, differentiable initial-data model that combines sparse-grid spectral interpolation with Newton refinement over a family of binary configurations. Interpolation is used only to provide warm starts for the underlying elliptic solver, rather than to replace it. A small number of Newton iterations refines each interpolated solution to a discrete, row-equilibrated constraint residual $\|R\|_\infty\le10^{-10}$, independent of the interpolation error, so that every returned initial-data set satisfies the discretized constraint to that tolerance. Our JAX implementation provides analytic derivatives with respect to the physical parameters, enabling gradient-based parameter targeting, optimization, and sensitivity analysis. We demonstrate the method for quasi-circular binary-black-hole initial data using conformally flat Bowen–York punctures by constructing four-dimensional aligned-
spin and eight-dimensional general-
spin models. The resulting initial data are validated against TwoPunctures, and the method is applied to certified targeting of the physical Arnowitt–Deser–Misner mass and angular momentum and to effective-potential eccentricity reduction using a dedicated separation–tangential-momentum model.
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Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Post-fabrication trimming of a 1024-pixel, single-photon counting, Microwave Kinetic Inductance Detector array with a pixel pitch of 150 micron
Wilbert Ras-Vinke, Hessel Schulte, David J. Thoen et al. (+5 more)
Microwave Kinetic Inductance Detectors are superconducting resonators capable of single-
photon counting with energy resolving capability at visible and near-infrared wavelengths. Their zero read noise, extremely low dark counts, and compatibility with frequency-division multiplexing make them well suited for large imaging arrays. The detector yield of these arrays is often limited by the fabrication-induced frequency scatter leading to resonator collisions. We find that the tight packing of the pixels can add significant frequency scatter as well. We developed a post-fabrication correction method that is suitable for tightly packed arrays with a pixel pitch of $150\ \mathrm{\mu m}$. We demonstrate this method on a 1024-pixel array multiplexed on a single octave of readout bandwidth and show a reduction in frequency scatter from $1.1\times 10^{-2}$ to $3.5\times 10^{-4}$ and an increase in yield from $76\%$ to $94\%$.
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All authors Wilbert Ras-Vinke, Hessel Schulte, David J. Thoen, Kevin Kouwenhoven, Steven A.H. de Rooij, Tonny A.H.M. Coppens, Jochem J.A. Baselmans, Pieter J. de Visser
Instrumentation and Methods for Astrophysics · Cross-listed from quant-ph
Multiparameter quantum bounds for entanglement-assisted aperture synthesis
Kalaga Madhav, Pieter Kok and Nic Scott
Entanglement-assisted optical interferometry promises diffraction-limited imaging over baselines where light cannot be physically combined, but existing theory treats only a single visibility on one two-station baseline. This work formulates the multiparameter estimation problem for an M-station array imaging an extended scene. A reduction lemma shows that the multimode
quantum Fisher information (QFI) equals the mean
photon number times the QFI of a single delocalized
photon, collapsing the problem to a finite-dimensional one. The local
photon-number superselection rule (SSR) erases all phase information from the bare state, while shared
entanglement restores a fraction f(r)=r/(1+r) of the QFI on a baseline supplied with r pairs – a factor shown to be achievable, since the reduced two-mode state of any pair is exactly the two-station weak-thermal state. The QFI
matrix and its mean Uhlmann
curvature reveal numerically that a point source is measurement-compatible, whereas for every extended-source model examined it is incompatible, the Holevo bound exceeding the symmetric-logarithmic-derivative (SLD) bound by up to ~74%. An explicit collective receiver – a global mode-sorting (
quantum Fourier transform) measurement – then attains a weighted variance within ~7% of the SLD bound and roughly an order of magnitude below an explicit pairwise receiver, and a noisy-resource advantage threshold gives the break-even baseline (~20 km for near-term parameters) beyond which repeater-distributed
entanglement beats direct transmission. Finally, the optimal allocation of a finite
entanglement budget is a convex program with a closed-form proportional (square-root-law) solution favoring low-visibility baselines. These results recast
quantum aperture synthesis as collective multiparameter estimation and give concrete design targets, illustrated on the CHARA array.
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Instrumentation and Methods for Astrophysics
Enabling New Discoveries with Machine Learning
Michelle Lochner
The next generation of
telescopes such as the Square Kilometre Array and the Vera C. Rubin Observatory will produce enormous quantities of data, too large for traditional analysis techniques. Machine learning has proven invaluable in handling massive data volumes and automating tasks traditionally done by human scientists. The question is, can machine learning also automate scientific discovery? Recent advances in the field have made this feasible but only when combined with expert human input through active learning. Astronomaly is a publicly available framework for active anomaly detection in astronomy. It learns to make recommendations of interesting sources to a user, allowing scientists to quickly uncover rare and new classes of objects in large
datasets. In this paper, we review some of the discoveries made using Astronomaly, discuss the latest deep learning-based approaches and explore the critical role of the cyber-human interface in unveiling
cosmic mysteries hidden in massive astronomical
datasets.
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Instrumentation and Methods for Astrophysics
Modelling Fourier filtering wavefront sensors for PSD-based methods: the AOPERA tool
Romain Fétick, Vincent Chambouleyron, Lisa-Marie Mazzolo et al. (+6 more)
Compensation of the atmospheric
turbulence thanks to adaptive optics (AO) has now become commonly used for VLT or ELT class
telescopes in order to retrieve a resolution close to their diffraction limit. Following the increasing trend of AO system, there is also a stronger necessity for simulations in order to understand and predict their performance facing different observing conditions, that are the
evolution of the atmospheric
turbulence or the diversity of AO guide source. The so-called PSD based methods are well adapted to the demand thanks to their simplicity and speed. Moreover, they provide a comprehensive breakdown error budget and impact on focal plane, that is of high interest especially in the case of extreme adaptive optics. Their drawback is the challenge to describe non-linear wavefront sensors (WFS) such as the pyramid WFS or the Zernike WFS. There is a necessity to develop fast yet accurate methods to describe the behaviour of AO systems including sensitive WFS. We thus develop a method to compute the AO system response (electromagnetic phase power spectral density, and point spread function) including the non-linear behaviour of the wavefront sensor within PSD-based numerical tools. Mathematical formalism to describe the FF-WFS sensitivity combined to non-linearity management greatly improve the accuracy of description of AO systems through numerical simulations. After a mathematical description of the method, its numerical implementation is compared with end-to-end simulations using the OOPAO tool. Indeed end-to-end simulations are reproducing the response of AO systems with high fidelity, especially regarding WFS sensitivity and non-linearity. Similarity of results for the fitting error, temporal error and noise error proves the validity of our method in managing
Fourier filtering WFS sensitivity and non-linearity.
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All authors Romain Fétick, Vincent Chambouleyron, Lisa-Marie Mazzolo, Christophe Vérinaud, Arnaud Striffling, Cédric Héritier-Salama, Benoit Neichel, Jean-Francois Sauvage, Thierry Fusco
Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.GA
Milky Way Structure from Double White Dwarf Gravitational-Wave Sources
Shao-Dong Zhao, Xue-Hao Zhang, Qun-Ying Xie et al. (+2 more)
The millihertz gravitational-wave sky will be dominated by $\sim10^{8}$ double white dwarfs while $\sim10^{4}$ be resolvable in the Milky Way, whose three-dimensional spatial distribution traces the
Galaxy's structural parameters. We present Galena, a hierarchical
Bayesian pipeline that recovers these parameters from a double white dwarf catalogue through an inhomogeneous Poisson-process likelihood. Each source's $3\times3$ Galactic position covariance is computed from the waveform Fisher information
matrix and propagated analytically through a $3\times5$ Jacobian; the resulting measurement-error convolution is factored into a pre-computed sparse weight
matrix, rendering the nested-sampling inference tractable. Applied to GBSIEVER-reported LISA Data Challenge sources ($N=2151$ after quality cuts), Galena recovers the disk scale length $R_d=2175^{+51}_{-52}$~pc and scale height $z_d=282^{+7}_{-7}$~pc, consistent with a canonical thin disk, together with the bulge fraction $A=0.187^{+0.011}_{-0.012}$ and bulge scale radius $R_b=773^{+26}_{-25}$~pc; the bulge fraction, now recovered much closer to the literature value of $0.25$ than in our earlier exact-position fit, is measured at $\sim6\%$ statistical precision. An independent particle-swarm optimisation of the same likelihood reproduces these values to within a fraction of a percent, supporting the attribution of the improvement to the Fisher-
matrix error propagation rather than to the sampler. The search-stage astrophysical prior improves per-source distance estimates but leaves the hierarchical inference essentially unchanged.
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All authors Shao-Dong Zhao, Xue-Hao Zhang, Qun-Ying Xie, Yu-Xiao Liu, Soumya D. Mohanty
Instrumentation and Methods for Astrophysics
First Very Long Baseline Interferometry Fringe Detection at 690GHz
Ming-Tang Chen, Geoffrey B. Crew, Dan Bintley et al. (+42 more)
We report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell
Telescope (JCMT) were carried out using ALMA's newly developed Band 9 phasing capability. Fringes were detected on the ALMA-APEX baseline during a scan of the
quasar J0423-0120, with a signal-to-noise ratio of ~12 and useful fringe recovery over solution intervals of order tens of seconds, representing the highest-frequency ground-based VLBI fringe detection reported to date. No fringes were found on the ALMA-JCMT baseline, despite excellent weather conditions, consistent with sensitivity predictions and supporting baseline performance models. The ALMA Phasing System maintained stable phasing at Band 9 for ~1-2 minutes before gradually degrading, indicating limitations under these observing conditions. Our analysis shows that, under excellent weather conditions, 690 GHz VLBI can still support fringe recovery over short solution intervals, despite rapid atmospheric phase fluctuations at these frequencies. This work validated key elements of near-terahertz VLBI operation and establishes a technical foundation for routine observations in the 690 GHz atmospheric window.
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All authors Ming-Tang Chen, Geoffrey B. Crew, Dan Bintley, Alan Roy, Keiichi Asada, Johnson Han, Kuan-Yu Liu, Chin-Shin Chang, Andrea McClöskey, Yiqing Song, Vincent Fish, Michael Lindqvist, Satoki Matsushita, Lynn D. Matthews, Hugo Messias, Jan F. Wagner, Ue-Li Pen, Derek Kubo, Teddy Huang, Philippe Raffin, Chih-Wei L. Huang, Pierre Martin-Cocher, Geoffrey C. Bower, Patrick Koch, Lisa Kewley, Timothy Norton, Nimesh Patel, Paul T. P. Ho, Per Friberg, Izumi Mizuno, Akil Marshall, Andrey M. Baryshev, Heino Falcke, Thomas Greve, Jacques Lepine, Manuel Fernández López, Silvina Cichowolski, Carlos Valotto, Ciriaco Goddi, Guillermo Giménez de Castro, Fátima Salete Correra, Marianne Vestergaard, Jes Kristian Jørgensen, Martin E. Pessah, Roman Gold
Instrumentation and Methods for Astrophysics · Cross-listed from physics.ins-det
Operation of a negative ion gas time projection chamber without electronegative fill gases
Lachlan J. McKie, Lindsey J. Bignell, Nicholas Adams et al. (+3 more)
The high fidelity reconstruction of particle tracks in micropatterned gaseous time projection chambers renders this technology ideal for future rare-event searches, including direction-sensitive dark matter experiments. Large drift distances are typically required for such experiments, so that the overall spatial resolution is limited by
diffusion. Negative ion drift exhibits lower
diffusion than electron drift and is thus an attractive option for realising a large-scale detector. The use of electronegative gases to create negative ions introduces technical challenges, most notably a reduction in gain when compared to conventional gas mixtures. In this study, we demonstrate a new method for negative ion generation via dissociative electron attachment using the conventional molecular fill gas CF$_4$. Our optical measurements of negative ion drift indicate electron attachment lengths of $<$1 mm and comparable gain to electron avalanches. The individual negative ion avalanches were also time-resolved, allowing the number of ions reaching the readout to be counted. We measure an improved energy resolution by single ion counting, relative to an integrated electron avalanche signal measured under identical gain conditions.
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All authors Lachlan J. McKie, Lindsey J. Bignell, Nicholas Adams, Victoria U. Bashu, Ferdos Dastgiri, Gregory J. Lane
Instrumentation and Methods for Astrophysics · Cross-listed from gr-qc
Clock-noise propagation and calibration for phase-locking configurations in space-based gravitational-wave detectors
Pan-Pan Wang and Cheng-Gang Shao
In space-based gravitational-wave detectors,
laser phase locking transfers the phase of weak received light to a local
laser and maintains the interspacecraft heterodyne frequencies within the phasemeter bandwidth. Fluctuations of the onboard ultrastable oscillators introduce clock noise into these heterodyne phase measurements, requiring additional calibration in time-delay interferometry (TDI). Existing formulations based on six independently formed one-way measurements do not explicitly describe the common-reference clock structure of a master–slave phase-locking configuration. In this work, we formulate clock-noise propagation and calibration directly for this configuration. Starting from carrier and sideband readouts, we derive the clock-noise couplings and construct an ordered sideband-calibration rule. The rule retains noncommuting delays and applies to two-branch TDI combinations satisfying propagation and clock-coefficient closure. For mutually independent onboard clocks with identical fractional-frequency noise spectra, we compare matched realizations with and without phase locking. In the adopted frozen equal-arm model, 45 second-generation combinations with up to 16 links considered here have smaller clock-noise residuals in the phase-locking realization throughout 0.1–10~mHz, before final clock calibration. Numerical simulations of two representative 16-link combinations reproduce the analytical spectra and verify the predicted reduction and calibration. These results show that the phase-locking realizations reduce the clock-noise contribution before final calibration, while the cancellation of master-
laser phase noise still relies on TDI.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.EP
Hybrid Spin-Orbit Tomography for Earth-like Planets: Simultaneous Mapping of Static Surfaces and Dynamic Clouds from Multicolor Light Curves
Atsuki Kuwata and Hajime Kawahara
Photometric variability of directly imaged
exoplanets encodes information on both persistent surface features and time-variable phenomena such as clouds. We present Hybrid
Spin-Orbit
Tomography, a method that simultaneously retrieves multiple static components and a single dynamic component, together with their reflection spectra, from multiband photometric variability. The method integrates spectral unmixing and dynamic
spin-orbit
tomography by introducing a time-dependent component into the forward model. We employ sparse regularization for static surface distributions, volume regularization for reflection spectra, and a Kronecker-sum kernel regularization for the dynamic component. Applying the method to a toy Earth model, we successfully recover static surface distributions together with a single time-dependent cloud component. Furthermore, we apply the method to DSCOVR/EPIC observations of Earth and retrieve a dynamic component consistent with real cloud distributions, together with components broadly interpretable as oceans, vegetation, and land surfaces. Relative to static
spin-orbit unmixing, the hybrid model substantially reduces the residual scatter of the multiband light curves, demonstrating that explicit treatment of dynamic components improves global mapping from color variability. These results provide a step toward the simultaneous
retrieval of static and dynamic planetary components, while highlighting the need for more physical cloud-surface masking models and uncertainty quantification.
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Instrumentation and Methods for Astrophysics · Cross-listed from astro-ph.SR
Automated Detection of Double-Lined Spectroscopic Binaries in High-Resolution Spectra and a Probabilistic Analysis of Stellar Multiplicity
William B. Salazar, Steven Giacalone and Andrew W. Howard
The characterization of Sun-like
stars, including determining whether those
stars are single or have stellar companions, has become increasingly important for missions seeking
planets beyond the Solar System. With upcoming missions like the Habitable Worlds Observatory (HWO) on the horizon, vetting
stars for binarity and confirming potential targets as viable is essential precursor science. In this paper, we present an automated
algorithm that searches for double-lined spectroscopic binaries (SB2s) in high-resolution spectra. Using MOLUSC, we simulate realistic stellar populations to quantify the capability of
algorithm for detecting stellar companions around nearby
stars, with potential applications to HWO target
stars and Gaia DR4
planet-host candidates. In addition, we explore how the detection rate is influenced by complementary observations like high-resolution adaptive optics imaging and time-series radial velocities. We find that our SB2 detection
algorithm alone can rule out 46.1% of stellar-mass companions. High-resolution adaptive optics alone rules out 79.6% of stellar companions. Radial velocity surveys alone ruled out 98.4% and 98.7% for 5-year and 10-year surveys, respectively. When all three methods are combined, the probability of a typical nearby
star having a stellar companion is <1%. The combination of the methods allows us to better understand and resolve target lists for future surveys.
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Instrumentation and Methods for Astrophysics
A pilot study on the CSST astrometric capability: Detecting astrometric binaries with Gaia synergy via simulated data
Shangyu Wen, Shilong Liao, Zhaoxiang Qi et al. (+8 more)
Context. The China Space-station Survey
Telescope (CSST) will provide deep, wide-field epoch astrometry during its 10-year mission. Astrometric binary orbits constrain the masses of stellar and compact-object components. Orbital recovery depends on astrometric precision and temporal coverage. Combining CSST and Gaia data extends the baseline and improves binary detection. Aims. We evaluate CSST, Gaia, and joint astrometry for binary-candidate selection and 12-parameter (12p) orbit fitting at faint magnitudes ($g>17.8$). We also test how regular CSST cadences affect the yield of 12p fits satisfying our criteria. Methods. We constructed a mock catalog, simulated CSST and Gaia epoch astrometry, and fitted five-parameter (5p) single-
star models to derive astrometric diagnostics, proper-motion anomaly features, and observational-sampling features. A four-stage histogram-based gradient-boosting classifier used these features to select candidates for 12p orbit fitting and assessment. Results. On the independent test set, the classifier reaches a precision of 0.802 and a recall of 0.181 among eligible true binaries. In the scenario-specific fitted samples, joint astrometry raises the fiducial fraction from 6.76% for Gaia alone to 10.46%; for fitted binaries with $P_{\rm true}>15{\rm yr}$, it rises from 2.37% to 6.78%. The current CSST schedule yields few fiducial fits, while idealized regular cadences increase the yield mainly at $g\lesssim21$. Conclusions. In the simulation, joint CSST and Gaia epoch astrometry yields higher fractions of fitted unresolved binaries satisfying the stated criteria than Gaia-only solution. A practical strategy is to select candidates from 5p diagnostics and astrometric anomalies, obtain more regular CSST follow-up observations, and then fit 12p orbital models and apply the selection criteria.
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All authors Shangyu Wen, Shilong Liao, Zhaoxiang Qi, Zhensen Fu, Xiyan Peng, Ye Ding, Qiqi Wu, Qi Xu, Xun Sun, Keyu Zhu, Yong Yu